Here is some information for you, I hope it helps.
Cortland Line Company produced fishing line starting in 1915 and continue to do so today. During the early 1900's Brunswick was using Silk, and Irish Linen both were common fishing lines of the time to wrap cues, however in 1940's leather became the primary wrap materials used by them. Irish Linen fishing line became popular again with cue makers as a wrap material for pool cues in the late 1950's or the early 1960's. During that time frame George Balabushka started using Cortland Irish Linen for his pool cues. Originally George had used a Nylon wrap material for his cues, however, once he switched to Cortland many of his older customers had the Nylon wrap's removed and replaced with Irish linen because of this Balabushka cues with a Nylon wrap are rarely encountered.
George preferred to use Cortland #9 Irish which was White with Green Speck. The number that is attached to Irish Linen tells you how many individual strands were wrapped around each other to make a single line size, so basically Cortland #9 had 9 strand wrapped together or intertwined.
However, do not be confused there were other types of Irish Linen wrap materials used in the late 1960's and through the 1970's that looked similar to Cortland. One of the materials was called Ashland, it was also White with Green Speck, unless you know what to look for it can be very hard to tell.